The disclosure of Japanese Patent Application No. 2001-263494 filed on Aug. 31, 2001, including the specification, drawing, and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The present invention relates to a fuel injection device of a cylinder injection type internal combustion engine, which includes a main fuel injection valve for injecting a fuel into each combustion chamber of the engine with multiple cylinders, and being supplied with a high-pressure fuel from a high-pressure fuel channel, and to a fuel injection method thereof.
2. Description of Related Art
As for a spark ignition internal combustion engine for injecting a fuel into a combustion chamber or a so-called cylinder injection type internal combustion engine, an internal combustion engine, which includes an auxiliary fuel injection valve for injecting a fuel into an intake channel in addition to a main fuel injection valve for injecting the fuel into a combustion chamber, has been well known (see, e.g., Japanese Patent Laid-Open Publication No. 2000-352335). In a fuel injection device of the internal combustion engine described above, a portion of the fuel, necessary when the engine is started, is injected from the auxiliary fuel injection valve. Next, the injected fuel is mixed with sucked air flowing in the intake channel, and the mixture is vaporized. Then, the vaporized mixture is introduced into the combustion chamber to ensure desirable starting performance even under cold conditions.
In the fuel injection device, the fuel, supplied from a feed pump, is pressurized by a high-pressure fuel pump and is supplied to the main fuel injection valve. This enables fuel injection for desirable atomization against a pressure in the combustion chamber. On the other hand, the auxiliary fuel injection valve introduces the low-pressure fuel supplied from the feed pump, and injects the low-pressure fuel into the intake channel since pressurizing the fuel is unnecessary.
However, in the fuel injection device above, vapor may be generated in a high-pressure fuel pipe supplying the high-pressure fuel to the main fuel injection valve when the engine is started after high-temperature soaking. The vapor delays the pressurization of the fuel when the engine is started, so that the atomization of the fuel becomes insufficient, and the starting performance deteriorates.
In addition, it may be necessary to inject a small quantity of fuel from the main fuel injection valve to protect an exhaust emission-purifying catalyst when the engine is decelerating or returning from deceleration, or to prevent shocks when the engine is returning from deceleration. If a pressure in the high-pressure fuel pipe has not been lowered in advance in this case, the small quantity of fuel injection according to requirements cannot be gained, because of minimum injection time of the main fuel injection valve. As a result, fuel efficiency may be deteriorated, and it may not be possible to prevent the shocks when the engine is returning from deceleration.
To discharge the generated vapor described above or to lower a pressure of the high-pressure fuel, a special apparatus, which discharges the vapor and the high-pressure fuel from the high-pressure fuel pipe as desired, needs to be provided. However, if the apparatus is newly provided, the fuel injection device becomes complicated, increasing production cost.
It is one object of the present invention to provide a fuel injection device, which enables discharge of vapor in a high-pressure fuel channel and of a high-pressure fuel as needed without including a special apparatus, and a fuel injection method thereof.
A fuel injection device of a cylinder injection type engine, according to a first aspect of the present invention for achieving the object mentioned above, includes a main fuel injection valve which injects a fuel into each combustion chamber of the engine with plural cylinders, and pressurizes a low pressure fuel from a fuel supplying pump by a high-pressure fuel pump to supply the high-pressure fuel to a high-pressure fuel channel, and supplies the high-pressure fuel to the main fuel injection valve from the high-pressure fuel channel. Furthermore, the fuel injection device includes an auxiliary fuel injection valve which injects the fuel in an intake channel upstream of a branched point of the intake channel extending to each cylinder, and the auxiliary fuel injection valve is supplied with the high-pressure fuel from the high-pressure fuel channel.
The auxiliary fuel injection valve is supplied with the fuel from the high-pressure fuel channel, so that the fuel can be supplied to sucked air flowing in the intake channel with the use of the high-pressure fuel under cold conditions. In addition, when the engine is started after high-temperature soaking, vapor in the high-pressure channel can be discharged by opening the auxiliary fuel injection valve. Furthermore, in a case where the fuel pressure in the high-pressure fuel pump is decreased, a small quantity of fuel injection as desired can be realized immediately since a fuel pressure can be decreased by discharging the fuel in the high-pressure fuel channel as a result of opening the auxiliary fuel injection valve. This enables discharging of the vapor in a high-pressure fuel channel and the high-pressure fuel as desired without including a special apparatus for adjusting the fuel pressure.
In addition, an opening valve control of the auxiliary fuel injection valve can be performed to give assistance to adjustment of a fuel injection pressure of the main fuel injection valve.
With the opening valve control of the auxiliary fuel injection valve, the vapor is discharged from the high-pressure fuel channel, so that assistance can be given to increasing the fuel pressure by the high-pressure fuel pump. Furthermore, the fuel is discharged from the high-pressure fuel channel so that assistance can be given to decreasing the fuel pressure.
According to a second aspect of the present invention, a fuel injection method of a cylinder injection type engine is provided. The engine includes a main fuel injection valve which injects a fuel into each combustion chamber of the engine with plural cylinders, pressurizes a low pressure fuel from a fuel supplying pump by a high-pressure fuel pump to supply the high-pressure fuel to a high-pressure fuel channel, and supplies the high-pressure fuel to the main fuel injection valve from the high-pressure fuel channel. The fuel injection method includes closing the main fuel injection valve to cut off fuel injection into each combustion chamber in the cylinder injection type engine, injecting the high-pressure fuel into an intake channel upstream of a branched point of the intake channel extending to each cylinder through an auxiliary fuel injection valve from a high-pressure fuel channel when fuel injection from a main fuel injection valve is cut off.
The auxiliary fuel injection valve is supplied with the fuel from the high-pressure fuel channel so that the fuel can be supplied to sucked air flowing in the intake channel with the use of the high-pressure fuel under cold conditions. In addition, when the engine is started after high-temperature soaking, vapor in the high-pressure channel can be discharged by opening the auxiliary fuel injection valve. Furthermore, in a case where the fuel pressure in the high-pressure fuel pump is decreased as needed, a small quantity of fuel injection as desired can be realized immediately since a fuel pressure can be decreased by discharging the fuel in the high-pressure fuel channel as a result of opening the auxiliary fuel injection valve.